In recent years, vascular lesions have been treated by actively using a catheter because the surgical invasion is very small. In the manual operation of using a catheter for treatment, the catheter is delivered to the vicinity of a target area to perform diagnosis or treatment on the target area. Therefore, the catheter needs to have excellent operability (i.e., be easily maneuverable by an operator) so that the catheter can be quickly, reliably, and selectively inserted into a vascular system which has narrow and complicated patterns. The catheter also needs to have excellent indwelling ability so that the catheter can be fixed (i.e., held securely in place) in the vicinity of the target area when the diagnosis or the treatment is performed. In addition, the catheter needs to offer a wide choice of catheter inserting portions, to reduce a diameter of the catheter to reduce the burden on a patient, facilitate and improve operability for inserting the catheter or the like, and particularly to minimize an outer diameter of the catheter as much as possible while maintaining a constant inner diameter.
For example, a micro-catheter is used to perform the diagnosis or the treatment on the target area by administering or injecting various therapeutic drugs, contrast agents, or the like used in vascular embolization, or the micro-catheter is used to perform embolization on the target area by filling a blood vessel with an embolus material. The micro-catheter has to be selectively introduced into the target area while being moved forward inside a peripheral blood vessel which has many bifurcated portions, which meanders in a complicated manner, and whose diameter is narrow, such as approximately 3 mm or smaller. Therefore, it is desirable to use a micro-catheter having operability which enables the micro-catheter to be inserted into the narrow blood vessel, and having the indwelling ability which enables the micro-catheter to be fixed to an arrangement position in the vicinity of the target area when the contrast agent or the like is used in the vicinity of the target area.
For example, the catheter disclosed in Japanese Patent Application Publication No. JP-A-2001-218851 (corresponding to US 2002/0022825 A1) includes a coil having a reinforcing effect embedded into a wall of a flexible and tubular catheter main body. According to the catheter disclosed in Japanese Patent Application Publication No. JP-A-2001-218851 described above, in order to improve the operability for inserting the catheter, an outer surface of the catheter main body is covered with a hydrophilic polymer material for lubricating the outer surface (e.g., see Paragraphs [0077] to [0081]). According to the catheter disclosed in Japanese Patent Application Publication No. JP-A-2001-218851, the outer surface is covered with this hydrophilic polymer material. Therefore, the catheter can be smoothly inserted into the target area inside an abdominal organ (for example, a liver) or the like, even if the catheter is inserted into the peripheral blood vessel which has many bifurcated portions, which meanders in a complicated manner, and whose diameter is narrow, such as approximately 3 mm or smaller.